Motion
Understanding Motion
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Motion refers to the change in position of an object with respect to its surroundings in a given period of time.
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When an object moves in a straight line with respect to its observer, it's in linear motion.
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When an object's distance from a certain point is constantly changing, it's in non-linear motion. Examples include circular and oscillating motion.
Distance, Displacement, Speed, and Velocity
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Distance is the total path travelled and has no direction, whereas displacement is the shortest distance from start to finish, and comes with a direction.
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Speed is how fast an object moves disregarding direction, while velocity is speed in a given direction.
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Velocity can be calculated by displacement divided by time.
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Average velocity and instantaneous velocity are two key concepts.
Acceleration
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Acceleration refers to the rate at which an object changes its velocity.
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An object is accelerating if it's changing direction even if its speed remains the same.
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Acceleration can be calculated by the change in velocity divided by the time taken for this change.
Graphs of Motion
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Motion is often plotted on displacement-time, velocity-time and acceleration-time graphs.
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On a displacement-time graph, the gradient indicates speed.
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On a velocity-time graph, the gradient indicates acceleration, while the area under the graph indicates displacement.
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On an acceleration-time graph, the area under the graph represents the change in velocity.
Newton's Laws of Motion
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Newton's First Law states that an object will stay at rest or in uniform motion in a straight line unless acted upon by an external force.
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Newton's Second Law states that the force exerted on an object equals its mass times its acceleration (F=ma).
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Newton's Third Law states that for every action, there is an equal and opposite reaction.
Gravitational Force
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The gravitational force exerted on an object is dependent on its mass and the mass of other objects around it.
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While gravity pulls objects towards each other, their movement can resist this pull due to inertia or other opposing forces (like friction).
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The acceleration due to gravity near the surface of the Earth is approximately 10 m/s².
Practical Applications and Calculations
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These concepts of motion are used in everyday life, from driving to sports to the functioning of machinery.
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Practice calculating velocity, acceleration, force, and displacement using different equations of motion.